Electrodynamic force-compensation pressure contacts for circuit breakers



June 4, 1963 A. L ELECTRODYNAMIC FORC ATOU R 3,092,699

E-CCMPE ATION Filed Dec. 17, 1959 Fig! Ll L2 4 Sheets-Sheet 1 Fig. 2

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P fikp L\ L-2 l L'\ L2 L L INVENTORI rLLafoa/g ATTORNEYS June 4, 1963 ALATOUR 3,092,699

ELECTRODYNAMIC FBRCE-COMPENSATION PRESSURE CONTACTS FOR CIRCUIT BREAKERSFiled Dec. 17, 1959 4 Sheets-Sheet 2 (NVENTOR A. La/our ATTORNEYS June4, 1963 A. LATOUR 3,092,699

ELECTRODYNAMIC FORCE-COMPENSATION PRESSURE CONTACTS FOR CIRCUIT BREAKERSFiled Dec. 17, 1959 4 Sheets-Sheet a INVENTOR 4. La/our TTORNEYS June 4,1963 A LATOUR 3,092,699

ELECTRODYNAMIC FERCE-CCMPENSATION PRESSURE CONTACTS FOR CIRCUIT BREAKERSFlled Dec. 17, 1959 4 Sheets-Sheet 4 INVENTOR 14. Lafow BY MDM ATTORNEYSELECTRODYNAMIC FORCE-COMPENSATION PRESSURE C ONTA CTS FOR CIRCUITBREAKERS Andr Latour, Grenoble, France, assignor to Ets Merlin 8:Ger-in, Grenoble, France Filed Dec. 17, 1959, Ser. No. 860,186 Claimspriority, application France Dec. 23, 1958 9 Claims. (Cl. 200-87) Thisinvention pertains to electrical contacts arrangements such as areemployed in circuit breakers, and especially to improvements in theapplication of electrodynamic forces as an aid to proper functioning ofsuch contacts.

In my prior US. Patent No. 2,821,594 I have described an electric switchcombining a stationary contact and a movable contact, and a stationaryand a movable conductor respectively terminating at said contacts andboth having substantially rectilinear length portions which extendparallel and adjacent to each other when the switch is closed; saidmovable conductor constituting the supporting arm of said movablecontact and being disposed in a position to react magnetically (in theclosed position of the contacts) with said stationary conductor, in sucha direction as to urge the movable contact against the stationarycontact. In those switches the two conductors, at least upon the initialopening movement of the contacts and during formation of an arc, form(with their ends nearest to the contacts, said contacts, and said are) aloop, whereby the magnetic forces of the current tend to expand saidloop and thus to repel the arc.

In FIGURES 14 to 16 and 17 to 19 of the patent, corresponding to thediagram of FIGURE 4 of the patent, I described a device in which asecond stationary conductor is connected in series with the first namedstationary conductor and extends parallel to the same, and is disposedin a position to react magnetically, in the closed position of thecontacts, with said movable conductor to urge the movable contactagainst the stationary contact.

I have now discovered that this patented device can be greatly improved,by modifications that will be understood from the following.

If we designate by i the current to be switched off, in the mostfavorable case the currents traversing the movable conductor, and thatbranch of the stationary conductor in which the current flows in thesame direction, are equal to i/ 2, so that the attractive force isproportional to i 4, whereas the repulsive force created by the otherbranch of the stationary conductor is proportional to i /2; thus, thetotal force which urges the movable contact against the stationarycontact is equal to ai /4+bi /2; a and b being constant parameters.

I have now found that, if we dispose the two parallel stationaryconductors electrically, relatively to the contacts, so as to have saidtwo parallel conductors connected in series with the movable conductor,the attractive force as well as the repulsive force are proportional to1' so that, all other things being equal, the total force which.

urges the movable contact against the fixed contact is equal to ai +biIf we assume that the lengths and the distances of the conductors arethe same in the two directions, sothat we may seta=b, we have in thefirst case, a total force equal to %ai and, in the second case, a totalforce equal to 2ai an improvement of at least 267%.

The invention will best be understood from consideration of thefollowing detailed specification of certain assassin Patented June 4,1963 ice I FIGURES 1 and 2 represent schematically and according to aknown arrangement, the path of the current in the incoming and outgoingconductors of the contact members.

FIGURES 3 and 4 show schematically the novel arrangement, according tothe invention, of the incoming and outgoing conductors.

FIGURES 5 and 6 show schematically another arrangement proceeding fromthe same inventive idea.

FIGURE 7 shows in side elevation, partly in section, an embodimentaccording to the schematic arrangement shown in FIGURES 3 and 4.

FIGURE 8 is a plan view of FIGURE 7.

FIGURE 9 represents in side elevation another form of execution of thecontact arrangement, still according to the schematic arrangement shownin FIGURES 3 and 4.

FIGURE 10 is a horizontal section view taken along the line 1l lt} ofFIGURE 9.

FIGURE 1 is a schematic elevational view of the conductors connected tothe contact members, taken in a plane perpendicular to the plane whereinthe contacts are moving. 4

FIGURE 2 is a side view of the same conductors, the arrangement as shownby FIGURES l and 2 being already shown in my US. Patent No. 2,821,594.In these figures, P represents, for instance, the surface of the fixedcontact member and p that of the movable contact member, L1, L2 theconductors carrying the current to the contact P, 1 the conductorcarrying away the current from the contact p. For a betterunderstanding, the movable contact 12 and its conductor 10 are not shownin FIGURE 1. It will be easily appreciated that the conductors L1, L2form, with the conductor 1, a closed loop, and that the repulsive forcewhich is produced between the conductor 1 and the conductors L1 and L2,by virtue of the current flowing in opposite direction in saidconductors, has for a consequence an increase in the contact pressurebetween P and p. One will be aware,

however, that owing to the fact that the conductors L1 and L2 are notlocated in the plane wherein the conductor 1 is moving, the forcesexerted on this latter by the two conductors L1 and L2 are oblique withrespect to the direction of the contact pressure, and that only theresultant force produced by the two oblique repulsive forces is locatedin the motion plane of contact p; that is, in the desired and usefuldirection. As these forces are relatively very oblique with respect tothe motion plane, the resultant vector force is, of course, very muchsmaller than the arithmetical sum of the two repulsive forces.

FIGURES 3 and 4 show, with the same reference numerals used in FIGURES 1and 2, an arrangement according to the invention.

One will observe that, in these figures, a conductor L, carrying acurrent flowing in the same direction as in the conductor 1, is locatedbehind the conductor 1. These currents create an attractive force havingthe same direction as the contact pressure, and which adds to therepulsive forces exerted by L1 and L2 on the conductor 1. Thisarrangement is particularly advantageous, due to the fact that owing toits position, the conductor L may be placed much nearer to the conductor1 than would be possible for the conductors L1 and L2, and thereby toobtain an attractive force much higher than the repulsive force exertedby said conductors L1 and L2. It will easily be appreciated, in FIGURE4, that the path described by the current flowing through the contacts Pand p has the form of the Greek letter (p.

As shown in FIGURES 5 and 6, it is possible to obtain much greatercompensation effects, together with a contact device of much smallerdimensions, by combining in series two arrangements similar to the oneshown in FIG- URES 3 and 4. So, thus, in FIGURE 6, the rear conductor Lis divided as above into two conductors Ll and LZ which are prolonged bytwo conductors LL, and return to the contact P by the conductors L1 andL2 placed in close proximity to the conductors L1 and L2.

One obtains, in this way, a kind of coil with two turns wound inparallel, in the middle of which the conductor 1 integral with thecontact p may freely move. It is obvious that, if so desired, more turnscan be provided in each half of this coil.

In comparison with the known arrangement, the new arrangement of thisinvention allows not only a multiplication of the forces ofcompensation, but is particularly advantageous when the two contactshave to withstand a rupturing arc, because in this case, the magneticfield created by the two coils provides an excellent means of obtainingmagnetic blow-out.

Although the loops shown in the various figures have a rectangularshape, it is obvious that when the maximum resistance to theelectrodynamic forces must be obtained, these coils may readily be givena circular shape.

FIGURE 7 is a schematic elevation and sectional view of the contactarrangement according to FIGURES 3 and 4, and FIGURE 8 is a plan view ofFIGURE 7. In these figures, the contact surface of the fixed contact Pis obtained by means of two deep-drawn shells I placed face to face. Atthe contact point, the edges of the shells form a recess into whichpenetrates the contact surface of the movable contact member 17, in sucha manner that at least two contact points are always obtained. Eachshell extends towards the bottom by virtue of a jaw 2. The two jawsforms the conductors L1 and L2 in FIGURES 3 and 4. In order to preventthe dispersion of the current in the jaws, and to establish a passage inthe peripheral zone situated on the right side of each jaw, one or moreslits 3, 4 and 5 are provided in the jaws. The jaws are fixed onto acentral piece 6 as by means of the rivets 7, 8, 9 and 10. The rivets 8,9 and 10 are provided with insulating sleeves and insulating washers sothat no current can flow from the piece 6 into the jaw 2 in the regionof said rivets 8, 9 and 10. On the contrary, the rivet 7, which exerts aclamping action on the two jaws 2, directly or through a metallicwasher, is not insulated. It is only in the neighborhood of the rivet 7that the current can flow from the piece 6 into the jaws 2.

The left end of the piece 6 is clamped between two flat pieces 11 as bymeans of the rivets 12, 13 and 14, the fiat pieces I]; being intended tocarry the incoming current of the circuit-breaker to the fixed contactat 1. Here again, the rivets l2 and 13 are provided with insulatingsleeves and insulating washers so that no current can fiow from the fiatpieces 11 into the piece 6 through these rivets. On the contrary, therivet 14, which exerts a clamping action between the pieces 11 and 6, isnot insulated. Therefore, the current flows from the pieces 11 into thepiece 6 only in the neighborhood of the rivet 14. The piece 6 isprovided with a certain number of slits 15 and 16 intended to force thecurrent to flow along its right side. It will be appreciated that thecurrent path thus obtained, as shown by the dotted lines, has the shapeshown in FIGURES 3 and 4.

The use of slits in pieces of flat shape allows one not only to obligethe current to flow along a predetermined path, but presentsparticularly interesting advantages from other standpoints, namely:

1) It allows one to obtain, at particular chosen points, a heavyconcentration of current which is very favorable for the creation ofstrong attractive or repulsive forces; and this without reducing themechanical resistance of this piece in the direction in which theseforces are acting.

(2) The cooling surface of these pieces is practically not at alldiminished by the slits, so that the heat prod duced in the regions ofheavy current concentration can be easily dissipated.

For these reasons, the use of slits or saw-cuts in conducting pieces offlat shape constitutes one feature of the present invention.

The movable contact may be constituted by two U- shaped pieces 17 placedface-to-face and assembled by rivets. At their upper end, these piecescover a lever 18 preferably made of light metal and fixed at its lowerend on an axis 21. In order to oblige the current to flow along thedesired path, an insulating cap 19 is provided between the end of thelever 18 and the U-shaped piece 17 whose lower extremity has the form ofa fork and is riveted onto the lever 18 as by means of the rivet 20.

The movable lever 18 can be displaced by a device actuated by thecontrol mechanism (not shown) of the circuit-breaker; for instance, bytwo interrupting levers 23. When the points P and p come into contact,the levers 23 continue their movement towards the left and tension thespring 22 which secures the contact pressure. Continuing their movementtowards the left of the figure, the levers 23 may, towards the end oftheir travel, come into contact with the main contact pieces 24 throughwhich most of the current will then flow. During the reverse movementthese contacts (23 and 24) part without forming an are because, at themoment of separation, all the current is directed to the points P and pbetween which the arc is initiated upon the separation of contacts 1 and17.

It will be appreciated that in the fixed contact the current can onlyreach the point P by way of the side walls of the shells 1' which are ata greater distance from the median plane than the point P itself (seeFIGURE 8). As a result, the current lines reaching the point P form abend which has for its effect to drive the roots of the arc, whatevertheir position, towards the inner edges of the shells, that is to say,towards the median plane itself. In this way, an automatic centering ofthe arc roots is obtained, by which the functioning of the interruptingdevice is considerably improved. For this reason, the arrangement asdescribed is also considered as a feature of the invention.

Moreover, it will be seen from FIGURE 8 that the edges of the two shells1 are not in contact but, on the contrary, are separated by an interval25 of appropriate width.

This arrangement allows the gases which are produced at the separationof the points P and p, and which may have an explosive force, to beevacuated into the slits 25 without exerting on the arc root-s anyaction impeding the centering of the same.

As already indicated, the contact pressure can be secured, as shown inFIGURE 7, by a spring 22 exerting a force on the movable contact 17. Thecontact pressure may, however, be obtained by a spring exerting a forceon the fixed contact. An arrangement of this kind is shown in FIGURES 9and 10. In these figures, the movable contact is shown at 26 as a fiatbar of rectangular section. The slits 27, 28 and 29 oblige the currentto flow in the left side of the contact bar 26. The fixed contact isformed by two flat pieces 30 (FIGURE 10) fixed on the axis 31, borne bya piece 32 formed by two bracket pieces, as shown in FIGURE 10. A spring33 secures, through the intermediary of a rod 34 and a fork 35, thecontact pressure between the pieces 30 and the movable contact 26. Thetravel of the contact pieces is limited by the stops 36 and 37. Asaw-cut 38 obliges the current to flow into the extreme right region ofthe piece 32. Under these conditions, the current is obliged to followapproximately the path as shown in dashed lines, this path correspondingclosely to the current path as shown in FIG- URES 3 and 4.

In order to avoid the possibility that the electrodynamic forces maydeform the contact 26 in the region weakened by the slits or saw-cuts,the latter may advantageously be filled with a suitable insulatingmaterial.

It will be appreciated that this kind of contact may advantageouslyreplace, in FIGURES 7 and 8, the contacts 23 and 24 which would not onlyobtain a compensation of the forces at the contact points themselves,but also completely protect the control mechanism of the circuit-breakeragainst the electrodynamic forces developed in the pivoting levers 23and 18.

What is claimed is:

1. In an electric switch, the combination of a stationary and a movablecontact, and of a stationary and a movable conductor respectively endingat said contacts and having respectively substantially rectilinearlength portions extending parallel and close to each other when theswitch is closed, said movable conductor constituting the carrying armof said movable contact and being disposed in position to reactmagnetically in closed position of the contacts with said stationaryconductor in a direction to urge said movable contact against saidstationary contact, the two conductors, at least upon initial openingmovement of the contacts and formation of an arc, forming with theirends, nearest to the contacts, said contacts and said arc, a loop,whereby the magnetic forces of the current tend to expand said loop andthus to repel the arc; at least one of said conductors includingserially connected portions leading the current in successively oppositedirections on opposite sides of the other conductor to its correspondingcontact.

2. In an electric switch, the combination of a stationary and a movablecontact, and a stationary and a movable conductor respectively ending atsaid contacts and both having substantial length portions extendingclose to each other when the switch is closed, said movable conductorconstituting the carrying support of said movable contact and beingdisposed in position to react magnetically in closed position or" thecontacts with said stationary conductor in a direction to urge saidmovable contact against said stationary contact, the two conductors,upon initial opening movement of the contacts and formation of an arc,forming with their ends nearest to the contacts, said contacts and saidarc, a loop, whereby the magnetic forces of the current tend to expandsaid loop and thus to repel the arc; at least one of said conductorsincluding serially connected portions leading the current insuccessively opposite directions on opposite sides of the otherconductor to its corresponding contact.

3. In an electric switch, the combination of a stationary and a movablecontact, and of a stationary and a movable conductor respectivelyterminating at said contacts and having respectively substantial lengthportions extending close to each other when the switch is closed, saidmovable conductor constituting the carrying support of said movablecontact and being disposed in position to react magnetically in theclosed position of the contacts with said stationary conductor in adirection to urge said movable contact against said stationary contact;at least one of said conductors including serially connected portionsleading the current in successively opposite directions on oppositesides of the other conductor to its corresponding contact.

4. The combination of claim 3, in which at least one of the conductorsand the associated contact are constituted by the contact member itself,being slotted to isolate the contact into portions, at least one ofwhich portions provides a current path substantially parallel to theconductor associated with the other contact.

5. The combination of claim 3, in which, in closed condition of thecontacts, one of said portions is connected electrically in parallelwith said movable conductor.

6. The combination of claim 3, in which said at least one of saidconductors includes at least four such serially connected portionsleading the current in successively opposite directions.

7. In an electric switch, the combination of a stationary and a movablecontact,a first conductor constituting the carrying arm of said movablecontact and traversed by the sarne current as the movable contact, asecond conductor traversed by a current flowing in the same direction asthe current flowing in the first conductor and disposed in a position toexert on said first conductor an attractive force tending to maintainsaid movable contact in closed position, a third conductor traversed bya current flowing in the opposite direction with regard to the directionof current flowing in said first conductor and disposed in a position toexert on said first conductor a repulsive force, tending to maintainsaid movable contact in closed position, said contacts being connectedserially between said first conductor, on the one hand, and said secondand third conductors on the other hand, in the closed position of theswitch.

8. In an electric switch, the combination of a stationary and a movablecontact, a first conductor constituting the carrying arm of said movablecontact and traversed by the same current as the movable contact, asecond conductor traversed by a current flowing in the same direction asthe current flowing in the first conductor and disposed in a position toexert on said first conductor an attractive force tending to maintainsaid movable contact in closed position, a third conductor traversed bya current flowing in the opposite direction with regard to the directionof the current flowing in said first conductor and disposed in aposition to exert on said first conductor a repulsive force, tending tomaintain said movable contact in closed position, said first conductorbeing mounted to travel during its opening movement into a positionwhere said second conductor exerts on said first conductor a repulsiveforce tending to increase the speed of separation of the contacts.

9. In an electric switch, the combination of a stationary and a movablecontact, a first conductor constituting the carrying arm of said movablecontact and traversed by the same current as the movable contact, asecond conductor traversed by a current flowing in the same direction asthe current flowing in the first conductor and disposed in a position toexert on said first conductor an attractive force tending to maintainsaid movable contact in closed position, a third conductor connected tosaid stationary contact and traversed by a current flowing in theopposite direction with regard to the direction of the current flowingin said first conductor and disposed in a position to exert on saidfirst conductor a repulsive force tending to maintain said movablecontact in closed position, said first conductor forming, immediatelyafter the separation of the contacts and the formation of an arc, withsaid third conductor, said contacts and said arc, a loop, wherein themagnetic forces of the current tend to expand said loop and thus torepel said arc.

References Cited in the file of this patent UNITED STATES PATENTS1,754,349 Bruhlmann Apr. 15, 1930 2,732,468 Curtis et a1. Ian. 24, 19562,821,594 Latour Jan. 28, 1958 FOREIGN PATENTS 534,048 Belgium Dec. 31,1954 560,368 Germany Oct. 1, 1932

1. IN AN ELECTRIC SWITCH, THE COMBINATION OF A STATIONARY AND A MOVABLECONTACT, AND OF A STATIONARY AND A MOVABLE CONDUCTOR RESPECTIVELY ENDINGAT SAID CONTACTS AND HAVING RESPECTIVELY SUBSTANTIALLY RECTILINEARLENGTH PORTIONS EXTENDING PARALLEL AND CLOSE TO EACH OTHER WHEN THESWITCH IS CLOSED, SAID MOVABLE CONDUCTOR CONSTITUTING THE CARRYING ARMOF SAID MOVABLE CONTACT AND BEING DISPOSED IN POSITION TO REACTMAGNETICALLY IN CLOSED POSITION OF THE CONTACTS WITH SAID STATIONARYCONDUCTOR IN A DIRECTION TO URGE SAID MOVABLE CONTACT AGAINST SAIDSTATIONARY CONTACT, THE TWO CONDUCTORS, AT LEAST UPON INITIAL OPENINGMOVEMENT OF THE CONTACTS AND FORMATION OF AN ARC, FORMING WITH THEIRENDS, NEAREST TO THE CONTACTS, SAID CONTACTS AND SAID ARC, A LOOP,WHEREBY THE MAGNETIC FORCES OF THE CURRENT TEND TO EXPAND SAID LOOP ANDTHUS TO REPEL THE ARC; AT LEAST ONE OF SAID CONDUCTORS INCLUDINGSERIALLY CONNECTED PORTIONS LEADING THE CURRENT IN SUC-